(1) Field of the invention
The present invention relates to laminates, more particularly to laminates having a high degree of abrasion resistance and suitable for table and counter tops, wall panels, floor surfacing, tableware and the like.
(2) Description of the prior art
Typically, laminates may be made from papers or fabrics by impregnating them with resins of various kinds, assembling several layers and consolidating the assembly into a unitary structure while converting the resin to a cured state. Resins used may be any selected from phenolics, aminoplasts, polyesters, polyurethanes, epoxy resins and the like. Consolidation of the layers to a unitary laminated structure may involve pressures ranging from essentially zero (with contact only between the layers comprising the final laminate) to 2000 lb. per sq. in. or more. Curing or setting of the resins may be accomplished at room temperature, or elevated temperatures (of the order of 150.degree.-180.degree. C.) to reduce the time required for curing.
The selection of the paper or fabric to be used, and the resin for impregnation is governed by the intended end-use of the finished laminate. For some end uses, surface decoration is not required or wanted, but in many instances colors and/or patterns are desired to add eye appeal to the finished laminate. While color and/or pattern decoration may be wanted for an outer surface of the laminate, the core or base functions primarily as a strengthening support, and may comprise wood, such as plywood, multiple layers of unbleached or dark colored paper or cloth, and may utilize dark colored, less expensive impregnating resins, such as phenolic resins.
When decorated laminates are desired, an outer surface layer, hereinafter called "decor," is used to cover the core layer or layers. This colored or decorated paper, may be pigmented with titanium dioxide and/or other opacifying pigments to mask the dark-colored core stock. The decor layer may be impregnated with a wide variety of resins, which may be applied to the decor in latex form, or as solutions in suitable solvents.
To impart wear and/or abrasion resistance to such decorated laminates, it has long been the practice to place a resin-impregnated surfacing paper, hereinafter called "overlay" over the decor sheet. Upon consolidating the laminate, generally under heat and pressure, the overlay sheet becomes transparent, permitting the printed pattern to be seen. More recently, particles of silica have been incorporated in overlay papers to give added abrasion resistance to laminates incorporating them. Likewise, printed decor papers have been coated with resin syrups containing abrasion resisting particles of silica, sometimes with added fibers or micro-crystalline cellulose. All the known prior art relating to abrasion resistant laminates applies a wear layer of some type over the printed pattern.